A sub-100 nW Power, Compact CTDSM with a Band-To-Band Tunnelling Loop Filter

This work presents a continuous-time delta-sigma modulator (CTDSM) deploying an experimentally demonstrated band-to-band-tunelling (BTBT) SOI MOSFET-based loop filter. With a compact, low-pass filter circuit and extremely low current in the BTBT regime, a loop filter implementation will provide optimality in terms of area and power performance. In literature for moderate-resolution CTDSMs, traditional loop filters are implemented with either fully passive, active, or hybrid integrators. These designs have a tight tradeoff in terms of area and power. The passive integrators have optimal power but suboptimal area, while the active integrators have optimal area and sub-optimal power consumption. The proposed work tries to break this tradeoff using BTBT regime loop filters. The CTDSM was designed in a GF45RFSOI technology and achieves a peak SNR/SNDR of 48.41 dB/47.94 dB for a 5 kHz bandwidth. The power consumption is 76.3 nW, with an area of 102.7 μm
²
— more than 100x area reduction over previous state-of-the-art moderate-precision CTDSM designs. This makes the proposed CTDSM extremely compact and power-efficient compared to traditional state-of-the-art moderate-resolution DSMs.